Unlocking the print of poly(L-lactic acid) by melt electrowriting for medical application

Melt electrowriting (MEW) is an advanced 3D printing technology to process high-resolution scaffolds. Although MEW has printed many biodegradable polymers, most of them have low printability, including poly(L-lactic acid) (PLLA) discussed in this study. While the print of PLLA scaffolds by MEW is elementarily realized, the scaffolds' limited structural change and mechanical properties influence their application. This study aims at improving the printability and the mechanical properties of the PLLA. To this end, the printability of the PLLA regarding jet lag angle and critical translation speed is investigated; the print limitation of PLLA is discovered, and the uniaxial and cyclic tensile tests for the scaffolds in linear and nonlinear structures are carried out. The results suggest that drying the PLLA before printing can significantly restrain polymer degradation to extend the printing period to approximately one day; planar PLLA scaffolds are able to reach 25 layers, 100 mu m interfiber distance, and 8 x 8 cm2 in dimension, and tubular PLLA scaffolds with 6 layers are successfully printed out; the mechanical properties of the PLLA scaffold reach the level of electrospun nonwoven fabrics. Thus, this study is a milestone work for the MEW technology to extend the printable materials.